Alternating-current shunt-commutator generator



Patenled .lune 1 2, A 1928.

UNITED STATES PATENT OFFICE.

.TosErn sLErnN, or swIssvALE, rmmsrnvnrn, saumon To WESTINGHOUSE ELECTRIC a mnrac'runme COMPANY, A Conrona'rron or rmsnvam ALTEBNATING-GUBENT SHUNT-COHIUTATOB GENERATOR.

Application illed December 14, 1920. Serial No. 430,615.

My invention relates to self-excited altermating-current generators and has particular relation to commutator-type machlnes having shunt-connected field windings.

I have discovered that an ordinary shuntconnected direct-current machine, when provided with a laminated ield member and a neutralizing winding, may be used to gen- 4 provided with a commutator and is driven from any suitable source (not shown). A shunt-connected field Winding 2 1s connected across the terminals of the armature, said field winding having in series therewith a regulating resistance 3 and a variable capacitance 4. The field circuit may also include a variable inductance 5. The machine may be provided with a neutralizing orcompensating winding 6, as is usual in alternatingcurreiit commutator machines.

The uses of such a generator'are numerous. Since the frequency is readily controlled by varying the capacitance or inductance of the field circuit, the generator may be employed to -supply power to induction motors, the

speed of which may be 4varied by the frequency of the generator currents. Such, a system is ideal for automobile drives.

Another application of my generator 1s to feed the wound secondary member of an induction motor the primary member of i which is connected across a constant-frequency system. The motor will then run at a speed corresponding to the .difference or sum of the two frequencies supplied, according to the direction of phase rotation of the ter described may7 be determined by reference to Fig. 2. irst a saturation curve A is plotted forthe machine. To do this, the machine is driven at a constant speed, and alternating current of varying strength issupplied to the field winding. The abscisste of the curve are the field currents, and the ordinates are the energy components of the armature electromotive forces, that is, thetcomponents in phase with the field curren Finally, a straight line B is drawn, passing through the origin and having a slo equal to the ohmic resistance of the field and armature circuit. The point C at which said line cuts the saturation curve is the point at which the generator will run. The slope of the line B may readily be varied by m'eans of the resistance 3.

While I have shown my invention in a preferred form, it is to be understood that it is susceptible of various modiiications by those skilled in the art without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention l. An alternating-current generator comprising an armature core of magnetic material having windings and a commutator, brushes bearing on said commutator, an exciting means including a core of magnetic material, a field Winding thereon and a serially connected condenser energized in shunt across the brushes, and a load circuit receiving energy from the brushes, the resistance of the shunt iield circuit being such that the voltage-current curve for said shunt iield circuit intersects the curve expressing the relation between the generated voltage and the field exciting current oi the machine.

2. An alternating-current generator comprising an armature core of magnetic material having windings` and a commutator, brushes bearing on said commutator, an eX- citing means including a core of magnetic material, a ield winding thereon, a iield rheostat and a serially connected condenser energized in shunt across the brushes, means for varying the relation between inductance and condensance in saidshunt field circuit, and a load circuit connected across the brushes.

shunt exciting field circuit, and a load cir- 10 cuit connected to the brushes and consisting solely of translating devices vof which the frequency is determined by said generator. .In testimony whereof, I have hereunto subscribed my name this 3rd day of Decem- 15 ber, 1920.

JOSEPH SLEPIAN. 

